Radial head orthopedic implant apparatus and method of using same

ABSTRACT

An orthopedic implant apparatus, said apparatus comprising: a body, said body having a generally cylindrical shape and comprising a first material, a flat bottom surface, a concave upper surface disposed opposite said bottom surface, and a longitudinal axis disposed through the center of said body; a cylindrical bore, said bore disposed along said longitudinal axis through said top surface of said body; a cylindrical plug, said plug comprising a second material and disposed within said bore of said body; and at least one stem, said at least one stem connected to said bottom surface of said body.

BACKGROUND 1. Field of the Invention

The present invention relates generally to the field of orthopedicimplants. More particularly, the present invention relates to orthopedicradial head implants.

2. Description of the Related Art

Trauma to the elbow joint frequently involves damage to the ligamentoussupport of the elbow and fractures of the osseous structures responsiblefor the skeletal integrity of the elbow joint. The proximal aspect ofthe radius, or radial head, is frequently injured either in isolation orin combination with injury to other bony or ligamentous structures ofthe elbow joint. The radial head may also be fractured in associationwith injuries to the forearm axis, including disruptions of theinterosseous membrane between the radius and the ulna. Whether inisolation or in combination with other injuries, fractures of the radialhead can be difficult to treat.

Fractures of the radial head are either reconstructable orunreconstructable. Despite various technical advances in thereconstruction of radial head fractures, a certain percentage offractures are not amenable to reconstruction due to the degreecomminution or severity of the fracture. In general, unreconstructableradial head fractures result from high energy trauma and are thereforefrequently associated with significant injuries to other osseous orligamentous structures of the elbow joint or forearm. In these cases,restoration of the stabilizing function of the radial head is criticalto allow the ligaments of the elbow or forearm to heal in appropriaterelationships, thereby restoring stability to the elbow or forearm. Thisstabilizing function depends, in part, upon re-establishing theappropriate distance between the capitellum and the proximal shaft ofthe radius.

The first widely used prosthetic radial head was introduced in the1970's and was composed of silicone. Silicone implants placed in variousjoints throughout the body led to “silicone synovitis,” in which thesilicone induces an inflammatory response within the joint. Further,silicone radial head prostheses were found to be incapable of resistingthe stresses to which the radial head is subjected, rendering it lessuseful in stabilizing the injured elbow or forearm.

The difficulties apparent with silicone led to experimentation withmetal radial head implants. These prostheses may be fashioned from asingle piece of metal or multiple pieces of metal (often titanium) andinclude a stem and a head portion. Most systems have an articularsurface (head) made of cobalt chrome and a stem made of titanium orcobalt chrome. However, a device may also comprise stainless steel.

The head portion is shaped to approximate the anatomy of the radialhead. These metallic prostheses are capable of resisting the compressivestresses to which the radial head is subjected, as has been demonstratedin several biomechanical studies. However, significant problems remainwith these prostheses.

Anatomic and radiographic studies of the dimensions of the radial headreveal a disparity with currently available metallic prostheses.Therefore, it has been difficult to restore appropriate anatomicalignments within the elbow. Therefore, restoration of the appropriaterelationship between the capitellum and proximal shaft of the radius hasbeen very difficult to achieve with these prostheses.

Thus, a need exists for new radial head implant devices Exemplary priorart devices are shown below.

U.S. Pat. No. 9,763,792 discloses a system for replacing an end of abone, such as a radial bone, with a prosthesis. In exemplaryembodiments, the prosthesis is a radial head prosthesis having a stemportion and a head portion. The head portion may be configured to be (a)placed onto the stem portion by movement of the head and stem portionsrelative to one another transverse to a longitudinal axis of the stemportion, and then (b) rotated with respect to the stem portion toproduce friction that firmly attaches the head portion to the stemportion.

U.S. Pat. No. 9,668,869 discloses an elbow prosthesis including a stemstructure and an articulating component. The stem structure is operableto be positioned in a bone of a joint and includes a stem portion and aC-shaped body portion. The stem portion is operable to be positioned inthe bone. The C-shaped body portion includes a first articulatingsurface bound by a medial wall and a lateral wall. The medial andlateral walls are separated by a first distance. The articulatingcomponent includes a second articulating surface positioned between amedial side surface and a lateral side surface. The medial and lateralside surfaces are separated by a second distance that is less than thefirst distance. The second articulating surface is configured toslidably communicate in a medial/lateral direction along the firstarticulating surface of the C-shaped body portion.

U.S. Pat. No. 9,655,726 discloses a radial-capitellar implant forsurgical replacement of the capitellum of the humerus and, optionally,the head of the radius. The radial-capitellar implant includes acapitellar implant or surface replacement arthroplasty of the capitellumand a radial prosthesis for replacement of the head of the radius. Inone embodiment the radial prosthesis includes an articular head whichmoveable articulates with a stem implantable in the radius.

U.S. Pat. No. 9,632,28 discloses a radial head implant including a head,a stem, and a locking mechanism, whereby the head laterally engages thestem, and an instrument for implanting and removing such implant isdescribed.

U.S. Pat. No. 9,561,110 discloses an elbow prosthesis including acapitellar implant having an articulating head and a stem. Thearticulating head can have a first articulating surface positionedgenerally between a lateral side and a medial side. A passage can extendthrough the articulating head from the lateral side to the medial side.The articulating head can define a counterbore formed at the lateralside and that is concentric with the passage. According to otherfeatures, the elbow prosthesis can include a coronoid implant that has abody and a stem. The body can have a superior articulating surface thatincludes a central ridge and an anterior buttress. The central ridge canbe configured to accommodate articulation with a trochlea in animplanted position.

U.S. Pat. No. 9,039,779 discloses an elbow prosthesis having a firststem component attached to one of a humerus and an ulna, a second stemcomponent attached to the other of the humerus and the ulna, and a jointdisposed between and coupling the first stem component and the secondstem component to permit relative movement between the first stemcomponent and the second stem component about a first axis. The elbowprosthesis may additionally include a condyle extending from the jointand including an axis of rotation that is eccentric from the first axis.

U.S. Pat. No. 9,034,050 discloses an elbow prosthesis including acapitellar implant that has an articulating head and a stem. Thearticulating head can have a first substantially hemispherical portionand a second portion that collectively extend between lateral and medialsides of the articulating head and are separated by a plane. The firstand second portions can generally extend between the lateral and medialsides. The second portion can generally have an attachment lobe thatextends on the lateral side and that defines a passage therethrough. Thepassage can extend at least partially on the second portion.

U.S. Pat. No. 8,920,509 discloses a prosthesis system for replacement ofa head portion of a proximal radius can include an articulationcomponent having a first connection portion. A first head component canhave a second connection portion that connects to the first connectionportion. A second head component can have a third connection portionthat connects to the first connection portion. The second head componentcan have a distinct dimension from the first head component. A stemcomponent can include a fourth connection portion that connects witheither of the first or second head components. The stem component canhave a stem anchoring portion that connects to the radius.

U.S. Pat. No. 8,535,382 discloses a prosthesis system for replacement ofa head portion of a proximal radius. The system can include a firstpolymeric articulation component having a first locking portion and ametal head component having a second locking portion. The second lockingportion can mate with the first locking portion to form a first lockingmechanism to initially couple the first articulation component to thehead component. The head component can define a locking channel. Thesystem can also include a stem component having a protrusion receivablein the locking channel. The protrusion can define a bore, and the stemcomponent can be adapted to be coupled to the radius. The system canalso include a fastener received through the locking channel and intothe bore to provide a second locking mechanism that couples the headcomponent to the stem component.

U.S. Pat. No. 8,425,615 discloses a modular prosthesis system forreplacement of a head portion of a radius. The prosthesis systemincludes a head component having a first connection portion thatconnects to a second connection portion and a collar component havingthe second connection portion and a third connection portion. The systemalso includes a stem component including a fourth connection portionthat connects with the third connection portion, the stem componenthaving a stem anchoring portion that connects to the radius. The collarcomponent provides the modular geometry to the prosthesis without havingto have an increased number of head components and stem components withvariable lengths and angles.

U.S. Pat. No. 8,366,781 discloses a modular prosthesis system forreplacement of a head portion of a proximal radius includes a monolithicstem component, a head component, and a locking mechanism formed by thestem and head components. The stem component defines a stem anchoringportion having a longitudinal axis and configured to couple to theproximal radius, and a dovetail-shaped first mounting portion on a firstend face that extends in a first direction transverse to thelongitudinal axis. The head component has a dovetail-shaped secondmounting portion on a second end face opposite the first end faceslidably engaged with the first mounting portion along the firstdirection. One of the first and second mounting portions intersects thelongitudinal axis. The locking mechanism is formed at an interfacebetween the stem and head components and is engaged through relativetranslational movement between the stem and head components. A relatedmethod is provided.

U.S. Pat. No. 8,100,980 discloses an artificial elbow joint including ahumeral component made of metal and an ulnar component made of resinsfor replacing an elbow joint. The humeral component of this artificialelbow joint is configured by a substantially cylindrical trochlea and astem extending from the trochlea that is inserted into the humeral; andthe ulnar component is configured by a joint surface member whichreceives the trochlea of humeral component in a rotatable manner and astem which extends from the joint surface member and is inserted intothe ulna. The stem of the humeral component is curved gently downwardoverall so as to comply with the lordotic shape of the humeral, and thetrochlea is turnable about the centerline of the stem.

U.S. Pat. No. 7,641,695 discloses a modular endoprosthetic radial headimplant includes an end cap secured to a cannulated body held to bone bya fixation element. The fixation element supports the cannulated body ona resected radial bone end, for example. The fixation element of oneembodiment features a threaded stem with a spherical head. The stem fitsdistally into the cannulated body and extends through a hole formed bythe distal end of the cannulated body. The spherical head nests insidethe cannulated body. Polyaxial alignment between the cannulated body andthe fixation element is locked using a jam nut tightened inside thecannulated body. An end cap fits into place proximally on the cannulatedbody. The end cap is formed of a joint surface material to provide abearing surface.

U.S. Pat. No. 7,637,908 discloses a system for intramedullarysubchondral support fixation of radial head fractures is disclosed. Anillustrative embodiment of the system includes an insertion plate havinga head segment, a neck segment extending from the head segment, at leastone shaft segment extending from the neck segment and at least one tailsegment extending from the at least one shaft segment. A plurality offastener openings may be provided in the insertion plate and a pluralityof fasteners may extend through at least two of the plurality offastener openings, respectively. A method for intramedullary subchondralsupport fixation of radial head fractures is also disclosed.

U.S. Pat. No. 7,160,329 discloses a radial-capitellar implant forsurgical replacement of the capitellum of the humerus and, optionally,the head of the radius. The radial-capitellar implant includes acapitellar implant or surface replacement arthroplasty of the capitellumand a radial prosthesis for replacement of the head of the radius. Inone embodiment the radial prosthesis includes an articular head whichmoveable articulates with a stem implantable in the radius.

U.S. Pat. No. 6,656,225 discloses a modular prostheses system forreplacement of the radial head portion of the radius bone, and methodsfor its use are disclosed. The system comprises a stem componentcomprising an anchoring portion and a mounting portion, and a headcomponent having an open channel wherein the open channel is configuredto connect to the mounting portion along an assembly axis that istransverse to a longitudinal axis of the stem component.

What is needed in the art is a modular radial implant that provides theflexibility to prevent damage to the capitellum while maintaining thestrength of the fully metal device.

SUMMARY

In one exemplary embodiment, the present invention includes anorthopedic implant apparatus, said apparatus comprising: a body, saidbody having a generally cylindrical shape and comprising a firstmaterial, a flat bottom surface, a concave upper surface disposedopposite said bottom surface, and a longitudinal axis disposed throughthe center of said body; a cylindrical bore, said bore disposed alongsaid longitudinal axis through said top surface of said body; acylindrical plug, said plug comprising a second material and disposedwithin said bore of said body; and at least one stem, said at least onestem connected to said bottom surface of said body.

In another exemplary embodiment, the present invention includes anorthopedic implant apparatus, said apparatus comprising: a body, saidbody having a generally cylindrical shape, a flat bottom surface, a topsurface disposed opposite said bottom surface, and a longitudinal axisdisposed through the center of said body; an annular insert, said inserthaving a concave surface and a cylindrical bore disposed through thecenter of said insert, said insert disposed on said top surface of saidbody, said insert comprising a first material; a cylindrical plug, saidplug disposed within said bore of said insert, said insert comprising asecond material; and at least one stem, said at least one stem connectedto said bottom surface of said body.

In another exemplary embodiment, the present invention includes anorthopedic implant apparatus, said apparatus comprising: a body, saidbody having a generally cylindrical shape and comprising a firstmaterial, a flat bottom surface, a concave upper surface disposedopposite said bottom surface, and a longitudinal axis disposed throughthe center of said body; a plurality of plugs, each of said plugscomprising a hemispherical shape, said plugs disposed on top of andconnected to said concave upper surface of said body; and at least onestem, said at least one stem connected to said bottom surface of saidbody.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood more fully from the detaileddescription given hereinafter and from the accompanying drawings of thepreferred embodiment of the present invention, which, however, shouldnot be taken to limit the invention, but are for explanation andunderstanding only.

In the drawings:

FIG. 1 shows an exploded perspective view of an apparatus in accordancewith a first exemplary embodiment of the present invention.

FIG. 2 shows a top view of an apparatus in accordance with a firstexemplary embodiment of the present invention.

FIG. 3 shows a side perspective view of an apparatus in accordance witha first exemplary embodiment of the present invention.

FIG. 4 shows a bottom perspective view of an apparatus in accordancewith a first exemplary embodiment of the present invention.

FIG. 5 shows a side view of an apparatus in accordance with a firstexemplary embodiment of the present invention inserted into a radiusbone.

FIG. 6 shows an exploded perspective view of an apparatus in accordancewith a second exemplary embodiment of the present invention.

FIG. 7 shows a top perspective view of an apparatus in accordance with asecond exemplary embodiment of the present invention.

FIG. 8 shows a side perspective view of an apparatus in accordance witha second exemplary embodiment of the present invention.

FIG. 9 shows a bottom perspective view of an apparatus in accordancewith a second exemplary embodiment of the present invention.

FIG. 10 shows a side view of an apparatus in accordance with a secondexemplary embodiment of the present invention inserted into a radiusbone.

FIG. 11 shows an illustration of a difference between the secondembodiment and the prior art.

FIG. 12 shows an exploded perspective view of an apparatus in accordancewith a third exemplary embodiment of the present invention.

FIG. 13 shows a top view of an apparatus in accordance with a thirdexemplary embodiment of the present invention.

FIG. 14 shows a side perspective view of an apparatus in accordance witha third exemplary embodiment of the present invention.

FIG. 15 shows a bottom perspective view of an apparatus in accordancewith a third exemplary embodiment of the present invention.

FIG. 16 shows a side view of an apparatus in accordance with a thirdexemplary embodiment of the present invention inserted into a radiusbone.

Corresponding reference characters indicate corresponding partsthroughout the several views. The exemplary embodiments set forth hereinare not to be construed as limiting the scope of the invention in anymanner.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The present invention will be discussed hereinafter in detail in termsof various exemplary embodiments according to the present invention withreference to the accompanying drawings. In the following detaileddescription, numerous specific details are set forth in order to providea thorough understanding of the present invention. It will be obvious,however, to those skilled in the art that the present invention may bepracticed without these specific details. In other instances, well-knownstructures are not shown in detail to avoid unnecessary obscuring of thepresent invention.

Thus, all the implementations described below are exemplaryimplementations provided to enable persons skilled in the art to make oruse the embodiments of the disclosure and are not intended to limit thescope of the disclosure, which is defined by the claims. As used herein,the word “exemplary” or “illustrative” means “serving as an example,instance, or illustration.” Any implementation described herein as“exemplary” or “illustrative” is not necessarily to be construed aspreferred or advantageous over other implementations. Moreover, in thepresent description, the terms “upper”, “lower”, “left”, “rear”,“right”, “front”, “vertical”, “horizontal”, and derivatives thereofshall relate to the invention as oriented in FIG. 1.

Furthermore, there is no intention to be bound by any expressed orimplied theory presented in the preceding Technical Field, Background,Summary or the following detailed description. It is also to beunderstood that the specific devices and processes illustrated in theattached drawings, and described in the following specification, aresimply exemplary embodiments of the inventive concepts defined in theappended claims. Hence, specific dimensions and other physicalcharacteristics relating to the embodiments disclosed herein are not tobe considered as limiting, unless the claims expressly state otherwise.

While there are many acceptable exposure methods, the Kaplan interval ina line from the lateral epicondyle toward Lister's tubercle, with theforearm in neutral rotation, permits the collateral ligament to be leftintact. In fracture dislocations, the exposure is through the traumaticopening in the ligament complex. Proximally, the ECRL origin is releasedwith the anterior capsule to permit direct access to the front of theradial head.

Thus, the surgical technique for implanting a radial head devicegenerally comprises templating the radial head prior to surgery todetermine the appropriate level of resection; resecting the radial headwith a surgical saw as close to the surgical neck as possible; preparingthe canal for the stem using sequentially larger broaches; reaming theradial canal prepare the same for the implant; planing the neck of theradius to ensure a flat surface perpendicular to the canal for the headof the implant; inserting the trail implant into the radius to evaluatethe stem size, head diameter and head height; and replacing the trialimplant with the final implant.

Referring generally to FIGS. 1-4, in one exemplary embodiment, radialorthopedic implant apparatus 1000 generally comprises a body 100. Body100 is comprised of a biocompatible metal such as cobalt chrome,stainless steel, or titanium.

Referring still to FIGS. 1-4, body 100 of apparatus 1000 has a generallycylindrical shape and a flat bottom surface 110. Body 100 furthercomprises a concave upper surface 120 disposed opposite said bottomsurface 110.

Referring again to FIGS. 1-4, body 100 further comprises a longitudinalaxis (not shown) disposed through the center of body 100. Body 100further comprises a cylindrical bore 130. Bore 130 is disposed alongsaid longitudinal axis through said top surface 120 of body 100.

Referring again to FIGS. 1-4, apparatus 1000 further comprises acylindrical plug 140. Cylindrical plug 140 comprises a second materialdistinct from the material of body 100 such as a biocompatible plasticpolymer or thermoset polymer. Plug 140 may comprise polyethylene,ultra-high molecular weight polyethylene, cross-linked polyethylene,PEEK, hydrogel, ceramic, or any other non-metal material havingmechanical properties suitable for a bearing component.

Referring still to FIGS. 1-4, body 100 of apparatus 1000 furthercomprises at least one stem 150. Stem 150 extends from bottom surface110 of body 100 in a direction opposite top surface 120 of body 100.Stem 150 may comprise a smooth surface for movement within the radius ora porous surface or bone growth promoting material for fixation withinthe bone. It is further contemplated that a plurality of stems 150 maybe provided to attach body 100 to a human radius. In alternativeembodiments, other known means may be used to attach body 100 to a bone.

Referring now to FIG. 5, there is shown a side view of apparatus 1000 inaccordance with an exemplary embodiment of the present invention. Asillustrated in FIG. 5, apparatus 1000 is inserted into theintramedullary canal of a radial bone.

Referring generally to FIGS. 6-9, in another exemplary embodiment,radial orthopedic implant apparatus 1001 generally comprises a body 101.Body 101 is comprised of a biocompatible metal such as cobalt chrome,stainless steel, or titanium.

Referring still to FIGS. 6-9, body 101 of apparatus 1001 has a generallycylindrical shape and a flat bottom surface 111. Body 101 furthercomprises a concave upper surface 121 disposed opposite said bottomsurface 111.

Referring again to FIGS. 6-9, body 101 further comprises a longitudinalaxis (not shown) disposed through the center of body 101. Body 101further comprises a cylindrical peg 131. Peg 131 is disposed along saidlongitudinal axis through said top surface 121 of body 101. Peg 131extends from body 101 in the direction of upper surface 121 andcomprises the same material as body 101.

Referring again to FIGS. 6-9, body 101 of apparatus 1001 furthercomprises a cylindrical ring 161. Cylindrical ring 161 comprises asecond material distinct from the material of body 101 such as abiocompatible plastic polymer or thermoset polymer. Ring 161 maycomprise polyethylene, ultra-high molecular weight polyethylene,cross-linked polyethylene, PEEK, hydrogel, ceramic, or any othernon-metal material having mechanical properties suitable for a bearingcomponent. As illustrated in FIGS. 7-9, ring 161 is disposed on the topsurface 121 of body 101 and peg 131 is disposed through the center ofring 161. Ring 161 further comprises a generally concave upper surfaceas illustrated in FIGS. 6-9.

Referring still to FIGS. 6-9, body 101 of apparatus 1001 furthercomprises at least one stem 151. Stem 151 extends from bottom surface110 of body 101 in a direction opposite top surface 121 of body 101.Stem 151 may comprise a smooth surface for movement within the radius ora porous surface or bone growth promoting material for fixation withinthe bone. It is further contemplated that a plurality of stems 151 maybe provided to attach body 101 to a human radius. In alternativeembodiments, other known means may be used to attach body 101 to a bone.

Referring now to FIG. 10, there is shown a side view of apparatus 1001in accordance with an exemplary embodiment of the present invention. Asillustrated in FIG. 10, apparatus 1001 is inserted into theintramedullary canal of a radial bone.

Referring to FIG. 11, advantageously, because ring 161 is conical ratherthan spherical, the capitellum will not initially reside in or touch thecentral metal until, through plastic material conformity, the capitellummay touch the central metal portion and “load sharing” would result.Alternatively, although not shown, ring 161 may be spherical if theradius is large enough to achieve the same result.

Referring next generally to FIGS. 12-15, in another exemplaryembodiment, radial orthopedic implant apparatus 1002 generally comprisesa body 102. Body 102 is comprised of a biocompatible metal such ascobalt chrome, stainless steel, or titanium.

Referring still to FIGS. 12-15, body 102 of apparatus 1002 has agenerally cylindrical shape and a flat bottom surface 112. Body 102further comprises a concave upper surface 122 disposed opposite saidbottom surface 112.

Referring again to FIGS. 12-15, body 102 of apparatus 1002 furthercomprises a plurality of plugs 142. Plugs 142 preferably have roundedtop surfaces and varying heights above upper surface 122 to maintain agenerally concave topology. Each plug 142 comprises a second materialdistinct from the material of body 102 such as a biocompatible plasticpolymer or thermoset polymer. Plugs 142 may comprise polyethylene,ultra-high molecular weight polyethylene, cross-linked polyethylene, orother non-metal materials as described above.

Referring still to FIGS. 12-15, body 102 of apparatus 1002 furthercomprises at least one stem 152. Stem 152 extends from bottom surface110 of body 102 in a direction opposite top surface 122 of body 102.Stem 152 may comprise a smooth surface, a porous surface, or bone growthpromoting materials. It is further contemplated that a plurality ofstems 152 may be provided to attach body 102 to a human radius.

While this invention has been described with respect to at least oneembodiment, the present invention can be further modified within thespirit and scope of this disclosure. This application is thereforeintended to cover any variations, uses, or adaptations of the inventionusing its general principles. Further, this application is intended tocover such departures from the present disclosure as come within knownor customary practice in the art to which this invention pertains andwhich fall within the limits of the appended claims.

The invention claimed is:
 1. A radial orthopedic implant apparatus, saidapparatus comprising: a body, said body having a generally cylindricalshape and comprising a first material, a flat bottom surface, a concaveupper surface disposed opposite said bottom surface, a longitudinal axisdisposed through the center of said body, and a centrally disposed borethat extends through the concave upper surface, wherein the bore isdisposed along said longitudinal axis through said upper surface of saidbody: an insert member comprising a second material different than thefirst material, the insert member configured to be inserted into thebore and disposed within the bore so as to couple to the body; and atleast one stem that extends from said bottom surface of said body,wherein the radial orthopedic implant apparatus is configured to beinserted into the medullary canal of a radial bone.
 2. The radialorthopedic implant apparatus of claim 1, wherein said first material isa biocompatible metal.
 3. The radial orthopedic implant apparatus ofclaim 2, wherein said biocompatible metal is selected from the groupconsisting of cobalt chrome, stainless steel, and titanium.
 4. Theradial orthopedic implant apparatus of claim 1, wherein said secondmaterial is a biocompatible plastic.
 5. The radial orthopedic implantapparatus of claim 4, wherein said biocompatible plastic is selectedfrom the group consisting of polyethylene, cross-linked polyethylene,hydrogel ceramic, PEEK, and ultra-high molecular weight polyethylene. 6.The radial orthopedic implant apparatus of claim 1, wherein said stem issmooth.
 7. The radial orthopedic implant apparatus of claim 1, whereinthe insert member and the bore are cylindrical.
 8. The radial orthopedicimplant apparatus of claim 1, wherein the bore is a single bore and theinsert member is a single insert member.
 9. The radial orthopedicimplant apparatus of claim 1, wherein the insert member is configured tobe inserted into the bore such that no portion of the insert memberextends out with respect to the concave upper surface in an upwarddirection that is defined from the flat bottom surface toward theconcave upper surface along the longitudinal axis.
 10. The radialorthopedic implant apparatus of claim 9, wherein no portion of theinsert member overlaps the concave upper surface along a directionparallel to the longitudinal axis.
 11. The radial orthopedic implantapparatus of claim 9, wherein the insert is sized substantially equal tothe bore in a plane that is oriented perpendicular to the longitudinalaxis.
 12. A radial orthopedic implant apparatus, said apparatuscomprising: a body, said body having a generally cylindrical shape andcomprising a first material, a flat bottom surface, a concave uppersurface disposed opposite said bottom surface, and a longitudinal axisdisposed through the center of said body: an insert member having abottom insert member surface and a upper insert member surface disposedopposite the bottom insert member surface, the insert member comprisinga second material different than the first material, the insert memberconfigured to be coupled to the body, wherein one of the body and theinsert member defines a bore, and the other of the body and the insertmember is configured to be inserted into the bore, such that the bottominsert member surface faces the body, and no portion of the upper insertmember surface is disposed outward with respect to the concave uppersurface of the body in an upward direction that is defined from the flatbottom surface toward the concave upper surface along the longitudinalaxis; at least one stem that extends from said bottom surface of saidbody, wherein the radial orthopedic implant apparatus is configured tobe inserted into the medullary canal of a radial bone.
 13. The radialorthopedic implant apparatus of claim 12, wherein said first material isa biocompatible metal.
 14. The radial orthopedic implant apparatus ofclaim 13, wherein said second material is a biocompatible plastic. 15.The radial orthopedic implant apparatus of claim 12, wherein the bodydefines a bore disposed along said longitudinal axis through said uppersurface of said body, and the insert member is sized and configured tobe disposed within the bore of the body.
 16. The radial orthopedicimplant apparatus of claim 15, wherein the insert member and the boreare cylindrical.
 17. The radial orthopedic implant apparatus of claim12, wherein the insert member is configured to be inserted into the boresuch that no portion of the insert member extends out with respect tothe concave upper surface in an upward direction that is defined fromthe flat bottom surface toward the concave upper surface along thelongitudinal axis.
 18. The radial orthopedic implant apparatus of claim17, wherein no portion of the insert member overlaps the concave uppersurface along a direction parallel to the longitudinal axis.
 19. Theradial orthopedic implant apparatus of claim 17, wherein the insert issized substantially equal to the bore in a plane that is orientedperpendicular to the longitudinal axis.